Multi-qubit device and quantum computer including the same

ABSTRACT

Multi-qubit devices and quantum computers including the same are provided. The multi-qubit device may include a first layer including a plurality of qubits; a second layer that is disposed on the first layer, and comprises a plurality of flux generating elements that apply flux to the plurality of qubits, a plurality of wire patterns that provide current to the plurality of flux generating elements, and a plurality of plugs that are disposed perpendicular to the plurality of flux generating elements and the plurality of wire patterns and interconnect the plurality of flux generating elements and the plurality of wire patterns. Each of the plurality of flux generating elements may be integrated with a corresponding one of the plurality of wire patterns and a corresponding one of the plurality of plugs.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2015-0186774, filed on Dec. 24, 2015 in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein byreference in its entirety.

BACKGROUND

1. Field

Exemplary embodiments relate to devices including quantum bits (qubits).

2. Description of the Related Art

A quantum computer may be defined as a computing apparatus using quantummechanical phenomena such as quantum superposition and quantumentanglement as operation principles thereof to process data. A unitdevice capable of storing data using quantum mechanical principles (orthe data itself) is called a quantum bit or a qubit, and may be used asa basic unit of data in a quantum computer.

A bit used in a typical data storage apparatus has a state of “0” or “1”but a qubit may simultaneously have states of “0” and “1” based onsuperposition. In addition, interaction is enabled among qubits based onentanglement. Due to the above characteristics of qubits, 2^(N) data maybe created using N qubits. Accordingly, if the number of qubits isincreased, the amount of data and the speed of processing may beincreased exponentially.

As interests in quantum computers are increased, research has beenconducted on various types of qubits. Qubits using a superconductor(i.e., superconducting qubits) may be easily produced as integratedcircuits. However, when a device including a plurality of qubits and aquantum computer using the same are implemented, various problems suchas undesired interference between constituent elements (devices) andnoise caused thereby should be solved.

SUMMARY

One or more exemplary embodiments provide multi-qubit devices capable ofeasily controlling the state of qubits using flux.

Further, one or more exemplary embodiments provide multi-qubit devicescapable of suppressing or preventing undesired interference betweenconstituent elements or noise caused thereby.

Further still, one or more exemplary embodiments provide multi-qubitdevices capable of increasing scalability thereof.

Further still, one or more exemplary embodiments provide multi-qubitdevices capable of increasing the degree of freedom in designing andaligning a plurality of qubits and peripheral devices/circuits thereof.

Further still, one or more exemplary embodiments provide quantumcomputers including the multi-qubit devices.

According to an aspect of an exemplary embodiment, there is provided amulti-qubit device including: a first layer structure disposed on asubstrate in a vertical direction of the multi-quit device andcomprising an array of a plurality of qubits; and a second layerstructure disposed between the substrate and the first layer structureand comprising a plurality of flux generating elements that apply fluxto the plurality of qubits in the vertical direction, wherein each ofthe plurality of qubits and each of the plurality of flux generatingelements corresponding to the plurality of qubits have centers that arealigned on substantially a same axis in the vertical direction.

Each of the plurality of qubits may be a superconducting qubit.

Each of the plurality of qubits may include at least one Josephsonjunction.

Each of the plurality of qubits may include a closed loop structure andat least one Josephson junction disposed on the closed loop structure,and may further include a first electrode line and a second electrodeline that extends in parallel to the first electrode from a side of theclosed loop structure.

Each of the plurality of flux generating elements may include apartially open loop structure and may further include a first wirepattern and a second wire pattern that extends in parallel to first wirepattern from the partially open loop structure.

The partially open loop structure may have a size less than or equal toa size of the closed loop structure.

The first and second wire patterns may extend in a direction in whichthe first and second electrode lines extend.

A distance between the first and second wire patterns may be less thanor equal to a distance between the first and second electrode lines.

Each of the plurality of flux generating elements may include asuperconducting material.

The multi-qubit device may further include an insulating layer that hasa thickness less than or equal to 100 nm and is disposed between theplurality of flux generating elements and the plurality of qubits.

The multi-qubit device may further include a plurality of wire patternsconnected to each of the plurality of flux generating elements, and theplurality of wire patterns may be disposed at a level different from alevel of the plurality of flux generating elements in the verticaldirection. The plurality of qubits may be disposed closer to theplurality of flux generating elements than to the plurality of wirepatterns.

The multi-qubit device may further include: an insulating layer that isdisposed between the plurality of flux generating elements and theplurality of wire patterns and includes a plurality of via holes; andplugs that are disposed in the via holes and interconnect the pluralityof flux generating elements and the plurality of wire patterns.

The insulating layer may have a thickness greater than equal to 100 nm.

The plurality of flux generating elements may be a plurality of firstflux generating elements, and the multi-qubit device may further includea third layer structure that faces the first layer structure wherein thefirst layer structure may be disposed between the second layer structureand the third layer structure. The third layer structure may include aplurality of second flux generating elements that applies flux to theplurality of qubits in the vertical direction.

The plurality of second flux generating elements may be symmetrical tothe plurality of first flux generating elements.

According to an aspect of another embodiment, there is provided aquantum computer including the multi-qubit device.

According to an aspect of another exemplary embodiment, there isprovided a multi-qubit device including: a layer structure including aplurality of qubits; a plurality of first flux generating elements thatare disposed under the layer structure in a vertical direction of themulti-quit device and apply flux to the plurality of qubits in thevertical direction; and a plurality of second flux generating elementsthat are disposed above and on the layer structure in the verticaldirection and apply flux to the plurality of qubits in the verticaldirection.

Each of the plurality of first flux generating elements may besymmetrical to each of the plurality of second flux generating elementscorresponding to the plurality of first flux generating elements.

Each of the plurality of qubits may include a closed loop structure andat least one Josephson junction disposed on the closed loop structure,and may further include a first electrode line and a second electrodeline that extends in parallel to the first electrode line from a side ofthe closed loop structure.

Each of the plurality of first flux generating elements may include afirst partially open loop structure, each of the plurality of secondflux generating elements may include a second partially open loopstructure. The multi-qubit device may further include a first wirepattern and a second wire pattern that extends in parallel to the firstwire pattern from the first partially open loop structure; and a thirdwire pattern and a fourth wire pattern that extends in parallel to thethird wire pattern from the second partially open loop structure.

The first and second partially open loop structures may have a size lessthan or equal to a size of the closed loop structure.

The first and second wire patterns and the third and fourth wirepatterns may extend in a direction in which the first and secondelectrode lines extend.

The first and second wire patterns may be disposed at a level differentfrom a level of the first partially open loop structure in the verticaldirection. In this case, at least a part of the first and second wirepatterns may extend in a direction different from a direction in whichthe first and second electrode lines extend.

The third and fourth wire patterns may be disposed at a level differentfrom a level of the second partially open loop structure in the verticaldirection. In this case, at least a part of the third and fourth wirepatterns may extend in a direction different from the direction of thefirst and second electrode lines.

The plurality of first flux generating elements may be provided on asubstrate, a first insulating layer covering the plurality of first fluxgenerating elements may be provided on the substrate, the plurality ofqubits may be provided on the first insulating layer, a secondinsulating layer covering the plurality of qubits may be provided on thefirst insulating layer, and the plurality of second flux generatingelements may be provided on the second insulating layer. The pluralityof first flux generating elements may be disposed on a substrate. Themulti-qubit device may further include: a first insulating layer that isdisposed on the substrate and covers the plurality of first fluxgenerating elements; and a second insulating layer that is disposed onthe first insulating layer and covers the plurality of qubits. Theplurality of qubits may be disposed on the first insulating layer andthe plurality of second flux generating elements are disposed on thesecond insulating layer.

According to an aspect of another exemplary embodiment, there isprovided a quantum computer including the multi-qubit device.

According to an aspect of another exemplary embodiment, there isprovided a multi-qubit device including: a first layer comprising aplurality of qubits; a second layer that is disposed on the first layer,and comprises a plurality of flux generating elements that apply flux tothe plurality of qubits, a plurality of wire patterns that providecurrent to the plurality of flux generating elements, and a plurality ofplugs that are disposed perpendicular to the plurality of fluxgenerating elements and the plurality of wire patterns and interconnectthe plurality of flux generating elements and the plurality of wirepatterns, wherein each of the plurality of flux generating elements isintegrated with a corresponding one of the plurality of wire patternsand a corresponding one of the plurality of plugs.

Each of the plurality of qubits and each of the plurality of fluxgenerating elements corresponding thereto may have shapes correspondingto each other and centers thereof may be aligned on substantially thesame vertical axis.

According to an aspect of another exemplary embodiment, a quantumcomputer includes the above multi-qubit device.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will be more apparent by describingcertain exemplary embodiments, with reference to the accompanyingdrawings, in which:

FIG. 1 is a perspective view of a multi-qubit device according to anexemplary embodiment;

FIG. 2 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 1;

FIG. 3 is a plan view of a qubit and a flux generating elementapplicable to a multi-qubit device, according to an exemplaryembodiment;

FIG. 4 is a plan view of a qubit and a flux generating elementapplicable to a multi-qubit device, according to another exemplaryembodiment;

FIG. 5 is a perspective view of a multi-qubit device according toanother exemplary embodiment;

FIG. 6 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 5;

FIG. 7 is a perspective view of a multi-qubit device according toanother exemplary embodiment;

FIG. 8 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 7;

FIG. 9 is a perspective view of a multi-qubit device according toanother exemplary embodiment;

FIG. 10 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 9;

FIG. 11 is a perspective view of a multi-qubit device according toanother exemplary embodiment;

FIG. 12 is a perspective view of a multi-qubit device according toanother exemplary embodiment; and

FIG. 13 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

DETAILED DESCRIPTION

Exemplary embodiments are described in greater detail below withreference to the accompanying drawings.

In the following description, like drawing reference numerals are usedfor like elements, even in different drawings. The matters defined inthe description, such as detailed construction and elements, areprovided to assist in a comprehensive understanding of the exemplaryembodiments. However, it is apparent that the exemplary embodiments canbe practiced without those specifically defined matters. Also,well-known functions or constructions are not described in detail sincethey would obscure the description with unnecessary detail.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. As used herein the term “and/or” includesany and all combinations of one or more of the associated listed items.

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps, operations,elements, and/or components, but do not preclude the presence oraddition of one or more other features, integers, steps, operations,elements, components, and/or groups thereof.

Example embodiments are described herein with reference tocross-sectional illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of exampleembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, example embodiments should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofexample embodiments.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments belong. Itwill be further understood that terms, such as those defined incommonly-used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand will not be interpreted in an idealized or overly formal senseunless expressly so defined herein.

FIG. 1 is a perspective view of a multi-qubit device according to anexemplary embodiment.

Referring to FIG. 1, the multi-qubit device includes a first layerstructure LL10 and a second layer structure LL20. The first layerstructure LL10 may include a plurality of qubits QB10, and an insulatinglayer NL10 on which the qubits QB10 are aligned. The qubits QB10 may bealigned two-dimensionally. The alignment scheme and the number of thequbits QB10 illustrated in FIG. 1 are examples and may vary.

The second layer structure LL20 may be disposed under the first layerstructure LL10. The second layer structure LL20 may include a pluralityof flux generating elements FG10 that apply flux to the qubits QB10. Theflux generating elements FG10 may be provided on an underlayer UL10.Thus, the second layer structure LL20 may include the underlayer UL10and the flux generating elements FG10 aligned thereon. Alternatively, anarray itself of the flux generating elements FG10 may be regarded as thesecond layer structure LL20. The underlayer UL10 may include asubstrate. Alternatively, an additional substrate may be furtherprovided under the underlayer UL10. Accordingly, the second layerstructure LL20 may be provided between the substrate and the first layerstructure LL10.

By applying a current to each flux generating element FG10, a flux,i.e., a magnetic flux, may be generated therefrom. The state of thequbit QB10 may be controlled using the flux. For example, the state ofthe qubit QB10 may be initialized or may be controlled for anotherpurpose using the flux. By controlling the intensity, direction,duration, or the like of the current applied to the flux generatingelement FG10, the intensity, direction, duration, or the like of theflux generated therefrom may be changed and the state of the qubit QB10may be tuned for a desired purpose.

The qubit QB10 and the flux generating element FG10 may correspond toeach other one to one. The qubit QB10 and the flux generating elementFG10 corresponding thereto may have shapes corresponding to each other.In other words, the qubit QB10 and the flux generating element FG10 mayhave the same shape or substantially the same shape. In addition, thequbit QB10 and the flux generating element FG10 corresponding theretomay be arranged to align the centers thereof on substantially the samevertical axis Z1. Further, the qubit QB10 and the flux generatingelement FG10 may face each other directly. The fact that the centers ofthe qubit QB10 and the flux generating element FG10 correspondingthereto are aligned on substantially the same vertical axis Z1 may meanthat, when viewed from the top, the centers thereof exactly or mostly(substantially) match. In this case, a certain level of error(tolerance) generated in a manufacturing process may be allowable. Forexample, when viewed from the top, the center of the qubit QB10 and thecenter of the flux generating element FG10 corresponding thereto mayexactly match or may have a deviation within about 20 nm or about 10 nm.Meanwhile, the width of each of the qubit QB10 and the flux generatingelement FG10 may be several μm to several ten μm. However, in somecases, the width of each of the qubit QB10 and the flux generatingelement FG10 may be less than about 1 μm.

The qubit QB10 may be, for example, a ‘superconducting qubit’ using asuperconductor. In this case, the qubit QB10 may include a loopstructure P10 formed of a superconductor. The loop structure P10 may bea closed loop structure. In addition, the qubit QB10 may further includeat least one Josephson junction J10 provided on the loop structure P10.The Josephson junction J10 may include two superconductors and adielectric layer provided therebetween. For convenience, the Josephsonjunction J10 is marked with a symbol X in FIG. 1. A description of thestructure (stack structure) of the Josephson junction J10 will be givenbelow with reference to FIG. 2. Although one qubit QB10 includes twoJosephson junctions J10 in FIG. 1, the number of Josephson junctions J10is not limited to two. Furthermore, the location of the Josephsonjunction J10 in the qubit QB10 may be changed.

The superconductor (superconducting material) of the qubit QB10 may be,for example, aluminum (Al), niobium (Nb), or lead (Pb). In other words,the superconductor included in the loop structure P10 and the Josephsonjunction J10 may be Al, Nb, or Pb. Charges (electrons) may move withoutresistance in the qubit QB10. That is, a superconducting current mayflow through the qubit QB10. Specifically, a Cooper pair consisting oftwo electrons may rotate along the loop structure P10 withoutresistance. In this case, the Cooper pair may tunnel through theJosephson junction J10 and may generate the superconducting currentirrespective of a tunneling barrier. Depending on the location or stateof the Cooper pair, the state of the qubit QB10 may be determined.

First and second electrode lines E10 and E20 may extend in parallel toeach other from a side of the loop structure P10. For example, the firstand second electrode lines E10 and E20 may extend in parallel to the Yaxis. The first and second electrode lines E10 and E20 may be called awire structure for applying an electrical signal to the qubit QB10. Thedistance between the first and second electrode lines E10 and E20 may beless than the X-direction width of the loop structure P10. The first andsecond electrode lines E10 and E20 may be formed of a superconductingmaterial, e.g., Al, Nb, or Pb. The first and second electrode lines E10and E20 may be formed of the same material as the loop structure P10 andmay be provided at a level (height) equal to the level (height) of theloop structure P10.

The flux generating element FG10 may have a shape corresponding to theshape of the qubit QB10. For example, the flux generating element FG10may have a loop structure R10. The loop structure R10 of the fluxgenerating element FG10 may be a partially open loop structure. The loopstructure R10 itself may be regarded as the flux generating elementFG10. The loop structure R10 may be formed of a superconductingmaterial, e.g., Al, Nb, or Pb. The center of the loop structure R10 andthe center of the loop structure P10 of the qubit QB10 correspondingthereto may be aligned on substantially the same vertical axis Z1. Theloop structure R10 of the flux generating element FG10 may have a sizeequal to or less than the size of the loop structure P10 of the qubitQB10. In this case, the flux generated by the flux generating elementFG10 may be focused on and applied to the loop structure P10 of thequbit QB10.

First and second wire patterns W10 and W20 may extend in parallel toeach other from two ends of the loop structure R10. The first and secondwire patterns W10 and W20 may apply an electrical signal (current) tothe loop structure R10. The first and second wire patterns W10 and W20may extend in a direction equal to the direction of the first and secondelectrode lines E10 and E20 (herein, a direction parallel to the Yaxis). In addition, the distance between the first and second wirepatterns W10 and W20 may be less than or equal to the distance betweenthe first and second electrode lines E10 and E20. The first and secondwire patterns W10 and W20 may be formed of the same superconductingmaterial as the loop structure R10, e.g., Al, Nb, or Pb. If the fluxgenerating element FG10 (i.e., R10) and the first and second wirepatterns W10 and W20 are formed of the superconducting material, a fluxmay be generated without generating heat or thermal noise due toapplication of a current. Accordingly, an increase in temperature of thequbit QB10 adjacent thereto may be prevented.

The loop structure P10 of the qubit QB10 may have a rectangular shape.For example, the loop structure P10 may have a square shape or asubstantially square shape. In this case, the loop structure R10 of theflux generating element FG10 may have a partially open square shape or ashape similar thereto. According to another exemplary embodiment, theloop structure P10 of the qubit QB10 may have a circular shape. At thistime, the loop structure R10 of the flux generating element FG10 mayhave a partially open circular shape. The shapes and locations of thequbit QB10 and the flux generating element FG10 will be described indetail below with reference to FIGS. 3 and 4.

In the current exemplary embodiment, the qubit QB10 and the fluxgenerating element FG10 are arranged to be spaced apart from each otherin a vertical direction (the Z direction), to have shapes correspondingto each other, and to align the centers thereof on substantially thesame vertical axis Z1. In this case, the flux generated by the fluxgenerating element FG10 may uniformly (or almost uniformly) influencethe qubit QB10 corresponding thereto. In addition, the first and secondelectrode lines E10 and E20 connected to the qubit QB10 and the firstand second wire patterns W10 and W20 connected to the flux generatingelement FG10 may also have shapes corresponding to each other and mayextend in the same direction. At this time, the first and second wirepatterns W10 and W20 may uniformly (or almost uniformly) influence thefirst and second electrode lines E10 and E20. In other words, the fluxgenerating element FG10 and the first and second wire patterns W10 andW20 may uniformly (or almost uniformly) influence the qubit QB10 and thefirst and second electrode lines E10 and E20 corresponding thereto.Accordingly, undesired interference or noise between constituentelements may be suppressed.

In addition, the flux generating element FG10 may have a size less thanor equal to the size of the qubit QB10, and the distance between thefirst and second wire patterns W10 and W20 may be less than or equal tothe distance between the first and second electrode lines E10 and E20.Accordingly, the flux generated by the flux generating element FG10 maybe focused on the qubit QB10 corresponding thereto and may hardlyinfluence the other qubits QB10. Similarly, electromagnetic influence ofthe first and second wire patterns W10 and W20 may be focused on onlythe first and second electrode lines E10 and E20 corresponding theretoand may hardly influence the other first and second electrode lines E10and E20 or the other qubits QB10. As such, the possibility of undesiredinterference or noise between constituent elements may be greatlyreduced.

If a flux generating element is arranged at a side of a qubit (which isreferred to as ‘asymmetric arrangement’ in this specification) unlikethe current exemplary embodiment, flux generated by the flux generatingelement may not uniformly influence the qubit corresponding thereto andmay easily generate noise to other adjacent qubits. In addition, wirepatterns connected to the flux generating element may also generate fluxnoise which influences other peripheral qubits or circuits. Accordingly,if the flux generating element is arranged at a side of the qubit, thelifetime of the qubit may be shortened and the reliability of a devicemay be reduced due to noise. Particularly, if the number of qubits isincreased, arrangement of qubits and flux generating elements may behard and complicated.

However, according to the current exemplary embodiment, the qubit QB10and the flux generating element FG10 may be arranged to be provided ondifferent layers, to have shapes corresponding to each other, and toalign the centers thereof on substantially the same vertical axis. Sucharrangement may be referred to as ‘symmetric arrangement’ or‘corresponding arrangement’ in this specification. In this case, asdescribed above, undesired interference or noise may be suppressed andthe lifetime and reliability of a device may be improved. In addition,the degree of freedom in designing a tunable multi-qubit device may begreatly improved.

FIG. 2 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 1. For convenience, only a unitstructure including one qubit QB11 and one flux generating element FG11corresponding thereto is illustrated in and described in relation toFIG. 2.

Referring to FIG. 2, the flux generating element FG11 may be disposed ona substrate SUB11. The substrate SUB11 may be formed of a material(insulating material) having a high quality factor (i.e., a high Qvalue) to minimize influence on a coherence state of the qubit QB11. Forexample, a sapphire substrate or a silicon (Si) substrate may be used asthe substrate SUB11. If the Si substrate is used, an insulating filmsuch as a silicon oxide (SiO₂) layer may be provided on a surfacethereof and then the flux generating element FG11 may be provided on theinsulating film. The flux generating element FG11 may be formed of asuperconducting material, e.g., Al, Nb, or Pb. First and second wirepatterns may also be provided at a level equal to the level of the fluxgenerating element FG11.

An insulating layer NL11 covering the flux generating element FG11 maybe disposed on the substrate SUB11. The insulating layer NL11 may beformed of silicon oxide, silicon nitride, or a dielectric materialhaving a dielectric constant greater than the dielectric constant ofsilicon nitride.

The qubit QB11 may be disposed on the insulating layer NL11. The qubitQB11 may include a loop structure P11 formed of a superconductingmaterial and may further include at least one Josephson junction J11provided on the loop structure P11. The Josephson junction J11 mayinclude two superconductors (a part of P11 and P11′) and a dielectriclayer D11 provided therebetween. Although one Josephson junction J11 isillustrated in FIG. 2, two or more Josephson junctions J11 may beprovided. The structure of the qubit QB11 may correspond to or besimilar to the structure of the qubit QB10 of FIG. 1. Thesuperconducting material included in the loop structure P11 and theJosephson junction J11 may be, for example, Al, Nb, or Pb. Thedielectric layer D11 may be, for example, Al₂O₃ but is not limitedthereto and may be variously changed.

A power source V11 may be electrically connected to the flux generatingelement FG11. The power source V11 may be connected to the fluxgenerating element FG11 through wire patterns (W10 and W20 of FIG. 1). Acurrent may be applied to the flux generating element FG11 using thepower source V11 and thus flux Fx1 may be generated by the fluxgenerating element FG11. The flux Fx1 may be applied to the qubit QB11in a vertical direction. For example, the flux Fx1 may be applied to theinside of the loop structure P11. Depending on the direction of thecurrent applied to the flux generating element FG11, the direction ofthe flux Fx1 may vary. The power source V11 may be, for example, avoltage source. In this case, the intensity of the flux Fx1 may becontrolled by adjusting the intensity of a voltage applied to the fluxgenerating element FG11 using the power source V11. An arrow marked onthe power source V11 means that the intensity of the voltage isadjustable. The sign (symbol) indicating the power source V11 in FIG. 2is an example and an actual configuration of the power source V11 may bevariously changed.

The thickness of the insulating layer NL11 provided between the fluxgenerating element FG11 and the qubit QB11 may be less than or equal toabout 100 nm. In this case, the flux Fx1 generated by the fluxgenerating element FG11 may be properly applied to and focused on thequbit QB11 corresponding thereto and may hardly influence the otherqubits. If the thickness of the insulating layer NL11 is excessivelylarge, the intensity of the flux Fx1 required to control the state ofthe qubit QB11 may be increased and thus power consumption may also beincreased. However, in some cases, the insulating layer NL11 may beprovided with a thickness greater than 100 nm. Furthermore, anadditional insulating layer (protective layer) covering the qubit QB11may be further provided on the insulating layer NL11.

Additionally, the flux generating element FG11 provided under the qubitQB11 as illustrated in FIG. 2 may be advantageous in terms of amanufacturing process. That is, a process of forming the flux generatingelement FG11 and then forming the qubit QB11 may be easier than thereverse process. In addition, if the flux generating element FG11 isformed and then the qubit QB11 is formed, the qubit QB11 may not beinfluenced by the process of forming the flux generating element FG11.

FIG. 3 is a plan view of a qubit QB1 and a flux generating element FG1applicable to a multi-qubit device, according to an exemplaryembodiment. FIG. 3 may correspond to a unit cell structure.

Referring to FIG. 3, the qubit QB1 and the flux generating element FG1corresponding thereto may be prepared. The qubit QB1 may have a closedloop structure P1. The loop structure P1 may have a rectangular shape,e.g., a square shape. The flux generating element FG1 may have apartially open loop structure R1. The loop structure R1 may have arectangular shape, e.g., a square shape. The loop structure P1 of thequbit QB1 and the loop structure R1 of the flux generating element FG1may have shapes corresponding to each other as described above, and thecenters thereof may be aligned on substantially the same vertical axis.The loop structure R1 of the flux generating element FG1 may have a sizeless than or equal to the size of the loop structure P1 of the qubitQB1.

First and second electrode lines E1 and E2 may be connected to the qubitQB1. In addition, first and second wire patterns W1 and W2 may beconnected to the flux generating element FG1. The first and secondelectrode lines E1 and E2 and the first and second wire patterns W1 andW2 may extend in the same direction. The distance between the first andsecond wire patterns W1 and W2 may be less than or equal to the distancebetween the first and second electrode lines E1 and E2. Referencenumeral J1 denotes at least one Josephson junction provided on the loopstructure P1 of the qubit QB1.

The qubit QB1 and the flux generating element FG1 of FIG. 3 may havecircular shapes instead of rectangular shapes. An example thereof isillustrated in FIG. 4. FIG. 4 is a plan view of a qubit QB2 and a fluxgenerating element FG2 applicable to a multi-qubit device, according toanother exemplary embodiment.

Referring to FIG. 4, the qubit QB2 and the flux generating element FG2corresponding thereto may have circular shapes. The qubit QB2 may have aclosed circular loop structure P2 and the flux generating element FG2may have a partially open circular loop structure R2. The loop structureP2 of the qubit QB2 and the loop structure R2 of the flux generatingelement FG2 may have shapes corresponding to each other, and the centersthereof may be aligned on substantially the same vertical axis. Firstand second electrode lines E3 and E4 may be connected to the qubit QB2,and first and second wire patterns W3 and W4 may be connected to theflux generating element FG2. The distance between the first and secondwire patterns W3 and W4 may be less than or equal to the distancebetween the first and second electrode lines E3 and E4. Referencenumeral J2 denotes at least one Josephson junction provided on the loopstructure P2 of the qubit QB2.

Although the qubits QB1 and QB2 and the flux generating elements FG1 andFG2 have rectangular or circular shapes in FIGS. 3 and 4, the shapesthereof may be variously changed. For example, the qubits QB1 and QB2and the flux generating elements FG1 and FG2 may have triangular shapes,five-or-more-sided polygonal shapes, or oval shapes.

FIG. 5 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

As shown in FIG. 5, the multi-qubit device includes the first layerstructure LL10 described above in relation to FIG. 1. The first layerstructure LL10 may include the insulating layer NL10 and the qubits QB10aligned thereon. Each qubit QB10 may include the loop structure P10 andat least one Josephson junction J10, and the first and second electrodelines E10 and E20 may be connected to the qubit QB10.

A second layer structure LL25 may be disposed under the first layerstructure LL10. The second layer structure LL25 may include a pluralityof flux generating elements FG15 that apply flux to the qubits QB10. Theflux generating elements FG15 may be the same as or similar to the fluxgenerating elements FG10 described above in relation to FIG. 1.Accordingly, each of the flux generating elements FG15 may include apartially open loop structure R15. In addition, the flux generatingelements FG15 may be provided on an underlayer UL15. The underlayer UL15may be an insulating layer.

The second layer structure LL25 may further include a plurality of wirepatterns W15 and W25 connected to each flux generating element FG15. Thewire patterns W15 and W25 may be provided at a level (height) differentfrom the level (height) of the flux generating element FG15. In thiscase, the wire patterns W15 and W25 may be provided far away from thequbit QB10 compared to the flux generating element FG15. The wirepatterns W15 and W25 may include a first wire pattern W15 and a secondwire pattern W25 connected to two ends of the flux generating elementFG15.

A plurality of via holes may be provided in the underlayer UL15, and aplurality of plugs C15 and C25 that interconnect the flux generatingelement FG15 and the wire patterns W15 and W25 may be provided in thevia holes. The plug C15 connected to the first wire pattern W15 may bereferred to as a first plug, and the plug C25 connected to the secondwire pattern W25 may be referred to as a second plug. For example, theentire portion of the plurality of plugs C15 and C25 may be buriedinside the second layer structure LL25 and the open loop structure R15may be disposed on the second layer structure LL25. A substrate orinsulator may be further provided under the second layer structure LL25.

As in the current exemplary embodiment, the flux generating element FG15and the wire patterns W15 and W25 connected thereto may be provided atdifferent levels (heights), and the wire patterns W15 and W25 may beprovided far away from the qubit QB10 compared to the flux generatingelement FG15. In this case, undesired interference or influence of thewire patterns W15 and W25 on the qubit QB10 may be further reduced. Inother words, generation of noise due to the wire patterns W15 and W25may be effectively suppressed or prevented. In addition, since the wirepatterns W15 and W25 are separately arranged in a new space (on a newlayer), the degree of freedom in design may be further improved. Forexample, in the current exemplary embodiment, since influence and/orinterference of the wire patterns W15 and W25 on the qubit QB10 aresuppressed or prevented, at least a part of the wire patterns W15 andW25 may be freely designed in a direction (extending direction)different from the direction of the first and second electrode lines E10and E20. Accordingly, the structure of FIG. 5 has various advantages interms of noise suppression and the degree of freedom in design.

FIG. 6 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 5.

Referring to FIG. 6, a plurality of wire patterns W12 and W22 may beprovided on a substrate SUB12. The substrate SUB12 may be the same as orsimilar to the substrate SUB11 described above in relation to FIG. 2. Afirst insulating layer NL12 covering the wire patterns W12 and W22 maybe provided on the substrate SUB12. The first insulating layer NL12 maybe formed of silicon oxide, silicon nitride, or a dielectric materialhaving a dielectric constant greater than the dielectric constant ofsilicon nitride. A flux generating element FG12 may be provided on thefirst insulating layer NL12. A plurality of via holes h12 and h22 may beprovided in the first insulating layer NL12, and a plurality of plugsC12 and C22 may be provided in the via holes h12 and h22. The plugs C12and C22 may interconnect the wire patterns W12 and W22 and the fluxgenerating element FG12. In addition, the plugs C12 and C22 may bedisposed to be perpendicular to the wire patterns W12 and W22 and theflux generating element FG12. The wire patterns W12 and W22, the plugsC12 and C22, and the flux generating element FG12 may be formed of asuperconducting material, e.g., Al, Nb, or Pb.

A second insulating layer NL22 may be disposed on the first insulatinglayer NL12, and a qubit QB12 may be disposed on the second insulatinglayer NL22. The second insulating layer NL22 may be the same as orsimilar to the insulating layer NL11 of FIG. 2. The qubit QB12 may bethe same as or similar to the qubit QB11 of FIG. 2. Accordingly, thequbit QB12 may include a loop structure P12 formed of a superconductingmaterial and may further include at least one Josephson junction J12provided on the loop structure P12. The Josephson junction J12 mayinclude two superconductors (a part of P12 and P12′) and a dielectriclayer D12 provided therebetween.

A power source V12 may be electrically connected to the flux generatingelement FG12. The power source V12 may be connected to the fluxgenerating element FG12 through the wire patterns W12 and W22 and theplugs C12 and C22. A current may be applied to the flux generatingelement FG12 using the power source V12 and thus flux Fx2 may begenerated by the flux generating element FG12. The flux Fx2 may beapplied to the qubit QB12 in a vertical direction.

In the current exemplary embodiment, the thickness of the firstinsulating layer NL12 may be greater than or equal to about 100 nm. Inthis case, the distance between the wire patterns W12 and W22 and thequbit QB12 may be increased and undesired interference or influencetherebetween may be effectively prevented or suppressed. Meanwhile, thethickness of the second insulating layer NL22 may be less than or equalto about 100 nm. In this case, the flux Fx2 generated by the fluxgenerating element FG12 may be properly applied to and focused on thequbit QB12 corresponding thereto and may hardly influence the otherqubits. As such, the thickness of the first insulating layer NL12 may begreater than the thickness of the second insulating layer NL22. However,the thicknesses of the first and second insulating layers NL12 and NL22are examples and appropriate thickness ranges of the first and secondinsulating layers NL12 and NL22 may vary.

FIG. 7 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

Referring to FIG. 7, the first layer structure LL10 described above inrelation to FIG. 1 may be provided. The first layer structure LL10 mayinclude the insulating layer NL10 and the qubits QB10 aligned thereon.Hereinafter, the insulating layer NL10 is referred to as a firstinsulating layer.

A second layer structure LL20 may be disposed under the first layerstructure LL10. The second layer structure LL20 may be the same as thesecond layer structure LL20 described above in relation to FIG. 1. Thesecond layer structure LL20 may include a plurality of flux generatingelements FG10 provided on an underlayer UL10. Hereinafter, the fluxgenerating elements FG10 are referred to as first flux generatingelements.

The multi-qubit device according to the current exemplary embodiment mayfurther include a third layer structure LL30 facing the second layerstructure LL20 by intervening the first layer structure LL10therebetween. Accordingly, the first layer structure LL10 may be locatedbetween the second and third layer structures LL20 and LL30. The thirdlayer structure LL30 may include a plurality of second flux generatingelements FG20 that apply flux to the qubits QB10 in a verticaldirection. The second flux generating elements FG20 may be provided on asecond insulating layer NL20. The second flux generating elements FG20may be symmetrical to the first flux generating elements FG10 byintervening the qubits QB10 therebetween. Accordingly, each second fluxgenerating element FG20 may have, for example, a partially open loopstructure R20. The shape and size of the partially open loop structureR20 may be the same as or similar to the shape and size of a loopstructure R10 of the first flux generating element FG10.

The third layer structure LL30 may further include a plurality of wirepatterns W30 and W40 connected to the second flux generating elementFG20. The wire patterns W30 and W40 may include a first wire pattern W30and a second wire pattern W40 connected to two ends of the second fluxgenerating element FG20. The extending direction of and the distancebetween the first and second wire patterns W30 and W40 may be the sameas or similar to the extending direction of and the distance between thefirst and second wire patterns W10 and W20 connected to the first fluxgenerating element FG10. Accordingly, the first and second wire patternsW30 and W40 connected to the second flux generating element FG20 mayextend in a direction equal to the direction of the first and secondelectrode lines E10 and E20, and the distance between the first andsecond wire patterns W30 and W40 may be less than or equal to thedistance between the first and second electrode lines E10 and E20.

FIG. 8 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 7.

Referring to FIG. 8, a first flux generating element FG13 may beprovided on a substrate SUB13. A first insulating layer NL13 coveringthe first flux generating element FG13 may be provided on the substrateSUB13. A qubit QB13 may be provided on the first insulating layer NL13.The qubit QB13 may include a loop structure P13 and at least oneJosephson junction J13 provided thereon. The Josephson junction J13 mayinclude two superconductors (a part of P13 and P13′) and a dielectriclayer D13 provided therebetween. The materials and configurations of thesubstrate SUB13, the first flux generating element FG13, the firstinsulating layer NL13, and the qubit QB13 may be the same as or similarto the materials and configurations of the substrate SUB11, the fluxgenerating element FG11, the insulating layer NL11, and the qubit QB11of FIG. 2.

A second insulating layer NL23 covering the qubit QB13 may be providedon the first insulating layer NL13. A second flux generating elementFG23 may be provided on the second insulating layer NL23. The secondflux generating element FG23 may be symmetrical to the first fluxgenerating element FG13 by intervening the qubit QB13 therebetween. Thesecond flux generating element FG23 may be formed of a superconductingmaterial.

A power source V13 may be electrically connected to the first and secondflux generating elements FG13 and FG23. A current may be applied to eachof the first and second flux generating elements FG13 and FG23 using thepower source V13 and flux Fx3 may be generated by the first and secondflux generating elements FG13 and FG23. The flux Fx3 may be applied tothe qubit QB13 in a vertical direction.

In the current exemplary embodiment, since the first and second fluxgenerating elements FG13 and FG23 are symmetrically arranged on andunder the qubit QB13 and the flux Fx3 is generated using the first andsecond flux generating elements FG13 and FG23, the intensity of thecurrent applied to each of the first and second flux generating elementsFG13 and FG23 to generate the flux Fx3 may be reduced by about ½. Thatis, compared to a case in which one flux generating element FG11 is usedas in FIG. 2, if two flux generating elements FG13 and FG23 are used asin FIG. 8, the intensity of the current applied to each of the first andsecond flux generating elements FG13 and FG23 may be reduced by ½. Inaddition, since the first and second flux generating elements FG13 andFG23 are symmetrical to each other by intervening the qubit QB13therebetween, the flux Fx3 generated thereby may be easily focused. Assuch, if the first and second flux generating elements FG13 and FG23 areused as in the current exemplary embodiment, generation of noise may beeffectively suppressed.

In some cases, instead of electrically connecting one power source V13to the first and second flux generating elements FG13 and FG23, a firstpower source may be electrically connected to the first flux generatingelement FG13 and a second power source may be electrically connected tothe second flux generating element FG23. In this case, the first andsecond flux generating elements FG13 and FG23 may be controlledindependently.

Meanwhile, the vertical distance between the first flux generatingelement FG13 and the qubit QB13 may be less than or equal to about 100nm. Similarly, the vertical distance between the second flux generatingelement FG23 and the qubit QB13 may be less than or equal to about 100nm. In other words, a height difference between a top surface of thefirst flux generating element FG13 and a bottom surface of the loopstructure P13 may be less than or equal to about 100 nm, and a heightdifference between a bottom surface of the second flux generatingelement FG23 and a top surface of the loop structure P13 may be lessthan or equal to about 100 nm. The thicknesses of the first and secondinsulating layers NL13 and NL23 may be determined to satisfy the abovecondition. However, appropriate thickness ranges of the first and secondinsulating layers NL13 and NL23 may vary.

FIG. 9 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

Referring to FIG. 9, the first layer structure LL10 described above inrelation to FIG. 5 may be provided. The first layer structure LL10 mayinclude the insulating layer NL10 (hereinafter referred to as a firstinsulating layer) and the qubits QB10 aligned thereon.

A second layer structure LL25 may be disposed under the first layerstructure LL10. The second layer structure LL25 may have the samestructure as the second layer structure LL25 described above in relationto FIG. 5. Accordingly, the second layer structure LL25 may include aplurality of flux generating elements FG15 (hereinafter referred to asfirst flux generating elements) that apply flux to the qubits QB10. Thefirst flux generating elements FG15 may be provided on an underlayerUL15. In addition, the second layer structure LL25 may further include aplurality of wire patterns W15 and W25 connected to each first fluxgenerating element FG15. The wire patterns W15 and W25 may be providedat a level (height) different from the level (height) of the first fluxgenerating element FG15. The wire patterns W15 and W25 may be providedfar away from the qubit QB10 compared to the first flux generatingelement FG15. A plurality of plugs C15 and C25 may be provided in aplurality of via holes provided in the underlayer UL15, and mayinterconnect the first flux generating element FG15 and the wirepatterns W15 and W25 corresponding thereto. For example, the entireportion of the plurality of plugs C15 and C25 may be buried inside thesecond layer structure LL25 and the open loop structure R15 may bedisposed on the second layer structure 25 to face the first layerstructure LL10.

A third layer structure LL35 may be disposed above the first layerstructure LL10. The third layer structure LL35 may be symmetrical to thesecond layer structure LL25 with respect to the first layer structureLL10. The third layer structure LL35 may include a plurality of secondflux generating elements FG25. Each second flux generating element FG25may have a partially open loop structure R25. In addition, the thirdlayer structure LL35 may further include a plurality of wire patternsW35 and W45 connected to the second flux generating element FG25. Thesecond flux generating element FG25 and the wire patterns W35 and W45corresponding thereto may be provided at different levels (heights). Thewire patterns W35 and W45 may be provided far away from the qubit QB10compared to the second flux generating element FG25. The third layerstructure LL35 may include the second flux generating element FG25disposed on a first side of a second insulating layer NL25 and mayinclude the wire patterns W35 and W45 disposed on a second side of thesecond insulating layer NL25. The first side of the second insulatinglayer NL25 may oppose the second side of the second insulating layerNL25, and the first side of the second insulating layer NL25 may facethe first layer structure LL10.

FIG. 10 is a cross-sectional view of a multi-qubit device correspondingto the exemplary embodiment of FIG. 9.

Referring to FIG. 10, a plurality of wire patterns W14 and W24 may beprovided on a substrate SUB14. A first insulating layer NL14 coveringthe wire patterns W14 and W24 may be provided on the substrate SUB14. Afirst flux generating element FG14 may be provided on the firstinsulating layer NL14. A plurality of via holes h14 and h24 may beprovided in the first insulating layer NL14, and a plurality of plugsC14 and C24 may be provided in the via holes h14 and h24. The plugs C14and C24 may interconnect the wire patterns W14 and W24 and the firstflux generating element FG14. In addition, the plugs C14 and C24 may bedisposed to be perpendicular to the wire patterns W14 and W24 and thefirst flux generating element FG14.

A second insulating layer NL24 may be provided on the first insulatinglayer NL14, and a qubit QB14 may be provided on the second insulatinglayer NL24. The qubit QB14 may be the same as or similar to the qubitQB11 described above in relation to FIG. 2. Accordingly, the qubit QB14may include a loop structure P14 formed of a superconducting materialand may further include at least one Josephson junction J14 provided onthe loop structure P14. The Josephson junction J14 may include twosuperconductors (a part of P14 and P14′) and a dielectric layer D14provided therebetween.

A third insulating layer NL34 covering the qubit QB14 may be provided onthe second insulating layer NL24. A second flux generating element FG24may be provided on the third insulating layer NL34. A fourth insulatinglayer NL44 covering the second flux generating element FG24 may beprovided on the third insulating layer NL34. A plurality of wirepatterns W34 and W44 connected to the second flux generating elementFG24 may be provided on the fourth insulating layer NL44. A plurality ofvia holes h34 and h44 may be provided in the fourth insulating layerNL44, and a plurality of plugs C34 and C44 may be provided in the viaholes h34 and h44. The plugs C34 and C44 may interconnect the secondflux generating element FG24 and the wire patterns W34 and W44.

A power source V14 may be electrically connected to the first and secondflux generating elements FG14 and FG24. Reference numeral Fx4 denotesflux generated by the first and second flux generating elements FG14 andFG24 and applied to the qubit QB14. Instead of electrically connectingone power source V14 to the first and second flux generating elementsFG14 and FG24, a first power source may be electrically connected to thefirst flux generating element FG14 and a second power source may beelectrically connected to the second flux generating element FG24.

The exemplary embodiment of FIG. 10 may simultaneously achieveadvantages of the exemplary embodiment described above in relation toFIGS. 5 and 6 and advantages of the exemplary embodiment described abovein relation to FIGS. 7 and 8. In other words, by separately providingthe two flux generating elements FG14 and FG24 on and under the qubitQB14, generation of noise may be effectively suppressed. At the sametime, by providing the lower wire patterns W14 and W24 and the upperwire patterns W34 and W44 on separate layers, generation of noise due tothe wire patterns W14, W24, W34, and W44 may be effectively preventedand the degree of freedom in design may be improved.

FIG. 11 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

Referring to FIG. 11, the multi-qubit device according to the currentexemplary embodiment may be similar to the multi-qubit device of FIG. 9.That is, lower wire patterns W15 and W25 and upper wire patterns W35 andW45 may be provided far away from a qubit QB10 using a via hole and plugstructure. In this case, since generation of noise due to the wirepatterns W15, W25, W35, and W45 is effectively prevented, the directionsof the wire patterns W15, W25, W35, and W45 may be freely designed.Accordingly, at least a part of the lower wire patterns W15 and W25 mayextend in a direction different from the direction of electrode linesE10 and E20 of the qubit QB10. Similarly, at least a part of the upperwire patterns W35 and W45 may also extend in a direction different fromthe direction of the electrode lines E10 and E20 of the qubit QB10.Therefore, according to the current exemplary embodiment, the degree offreedom in design may be improved.

According to another exemplary embodiment, a via hole and plug structuremay be applied to only one of upper and lower flux generating elements,and wire patterns connected to the flux generating element having thevia hole and plug structure may be designed in a direction differentfrom the direction of electrode lines of a qubit. Examples thereof areillustrated in FIGS. 12 and 13.

FIG. 12 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

Referring to FIG. 12, a second layer structure LL25 including aplurality of first flux generating elements FG15 may be provided under afirst layer structure LL10, and a third layer structure LL30 including aplurality of second flux generating elements FG20 may be provided abovethe first layer structure LL10. The first layer structure LL10 may bedisposed between the second layer structure LL25 and the third layerstructure LL30, and may be in contact with the second layer structureLL25 and the third layer structure LL30 when the manufacturing processof the multi-qubit device is complete. The first layer structure LL10may be the same as or similar to the first layer structure LL10described above in relation to FIGS. 7 and 9. The second layer structureLL25 may be the same as or similar to the second layer structure LL25 ofFIG. 9. The third layer structure LL30 may be the same as or similar tothe third layer structure LL30 of FIG. 7. Accordingly, the first layerstructure LL10 may include a plurality of qubits QB10 and first andsecond electrode lines E10 and E20 connected to each qubit QB10. Thesecond layer structure LL25 may include the first flux generatingelements FG15 and first and second wire patterns W15 and W25 connectedto each first flux generating element FG15. The first flux generatingelement FG15 and the first and second wire patterns W15 and W25 may beprovided at different heights and may be electrically connected to eachother by plugs C15 and C25 provided in via holes. The third layerstructure LL30 may include the second flux generating elements FG20 andfirst and second wire patterns W30 and W40 connected to each second fluxgenerating element FG20.

In the current exemplary embodiment, at least a part of the first andsecond wire patterns W15 and W25 connected to the first flux generatingelement FG15 may extend in a direction different from the direction ofthe first and second electrode lines E10 and E20. The first and secondwire patterns W30 and W40 connected to the second flux generatingelement FG20 may extend in a direction equal to the direction of thefirst and second electrode lines E10 and E20.

FIG. 13 is a perspective view of a multi-qubit device according toanother exemplary embodiment.

Referring to FIG. 13, a second layer structure LL20 including aplurality of first flux generating elements FG10 may be provided under afirst layer structure LL10, and a third layer structure LL35 including aplurality of second flux generating elements FG25 may be provided abovethe first layer structure LL10. The first layer structure LL10 may bedisposed between the second layer structure LL20 and the third layerstructure LL35, and may be in contact with the second layer structureLL20 and the third layer structure LL35 when the manufacturing processof the multi-qubit device is complete. The first layer structure LL10may be the same as or similar to the first layer structure LL10described above in relation to FIGS. 7 and 9. The second layer structureLL20 may be the same as or similar to the second layer structure LL20 ofFIG. 7. The third layer structure LL35 may be the same as or similar tothe third layer structure LL35 of FIG. 9. Accordingly, the first layerstructure LL10 may include a plurality of qubits QB10 and first andsecond electrode lines E10 and E20 connected to each qubit QB10. Thesecond layer structure LL20 may include the first flux generatingelements FG10 and first and second wire patterns W10 and W20 connectedto each first flux generating element FG10. The third layer structureLL35 may include the second flux generating elements FG25 and first andsecond wire patterns W35 and W45 connected to each second fluxgenerating element FG25. The second flux generating element FG25 and thefirst and second wire patterns W35 and W45 may be provided at differentheights and may be electrically connected to each other by plugs C35 andC45 provided in via holes.

In the current exemplary embodiment, the first and second wire patternsW10 and W20 of the first flux generating element FG10 may extend in adirection equal to the direction of the first and second electrode linesE10 and E20, and at least a part of the first and second wire patternsW35 and W45 of the second flux generating element FG25 may extend in adirection different from the direction of the first and second electrodelines E10 and E20.

A multi-qubit device according to the afore-described exemplaryembodiments may be used as a data storage apparatus of a quantumcomputer. Constituent elements of the quantum computer other than themulti-qubit device are well known and thus detailed descriptions thereofare not given herein. According to the exemplary embodiments, amulti-qubit device capable of easily controlling the state of qubitsusing flux may be implemented. In addition, a multi-qubit device capableof suppressing or preventing undesired interference between constituentelements or noise caused thereby may be implemented. Furthermore, amulti-qubit device capable of increasing the degree of freedom indesigning and aligning a plurality of qubits and peripheraldevices/circuits thereof may be implemented. Therefore, according to theexemplary embodiments, scalability of a multi-qubit device may beincreased. Using such a multi-qubit device, a quantum computer may beeasily implemented and performance thereof may be improved.Additionally, a multi-qubit device according to the afore-describedexemplary embodiments may also be applied to a quantum mechanicalapparatus/system other than a quantum computer.

The above detailed descriptions are not given to limit the scope of thepresent disclosure but should be understood as examples of embodiments.Specifically, it will be understood by those of ordinary skill in theart that the configurations of the multi-qubit devices described abovein relation to FIGS. 1 to 13 may be variously changed. For example, itwill be easily understood that the flux generating elements FG10 andFG11 may be provided on the qubits QB10 and QB11 and the alignmentscheme of the qubits QB10 and QB11 or the directions and structures ofthe electrode lines E10 and E20 and the wire patterns W10 and W20exemplary may be variously changed in FIGS. 1 and 2. In addition,throughout the embodiments, it will be understood that the structures ofqubits and flux generating elements may be variously changed and qubitsother than superconducting qubits may be used. Furthermore, it will beunderstood that a multi-qubit device according to the exemplaryembodiments may be applied to a quantum computer and a variety of otherquantum mechanical apparatuses/systems.

The foregoing exemplary embodiments are merely exemplary and are not tobe construed as limiting. The present teaching can be readily applied toother types of apparatuses. Also, the description of the exemplaryembodiments is intended to be illustrative, and not to limit the scopeof the claims, and many alternatives, modifications, and variations willbe apparent to those skilled in the art.

What is claimed is:
 1. A multi-qubit device comprising: a first layerstructure disposed on a substrate in a vertical direction of themulti-quit device and comprising an array of a plurality of qubits; anda second layer structure disposed between the substrate and the firstlayer structure and comprising a plurality of flux generating elementsthat apply flux to the plurality of qubits in the vertical direction,wherein each of the plurality of qubits and each of the plurality offlux generating elements corresponding to the plurality of qubits havecenters that are aligned on substantially a same axis in the verticaldirection.
 2. The multi-qubit device of claim 1, wherein each of theplurality of qubits is a superconducting qubit.
 3. The multi-qubitdevice of claim 1, wherein each of the plurality of qubits comprises atleast one Josephson junction.
 4. The multi-qubit device of claim 1,wherein each of the plurality of qubits comprises a closed loopstructure and at least one Josephson junction disposed on the closedloop structure, and further comprises a first electrode line and asecond electrode line that extends in parallel to the first electrodefrom a side of the closed loop structure.
 5. The multi-qubit device ofclaim 4, wherein each of the plurality of flux generating elementscomprises a partially open loop structure and further comprises a firstwire pattern and a second wire pattern that extends in parallel to firstwire pattern from the partially open loop structure.
 6. The multi-qubitdevice of claim 5, wherein the partially open loop structure has a sizeless than or equal to a size of the closed loop structure.
 7. Themulti-qubit device of claim 5, wherein the first and second wirepatterns extend in a direction in which the first and second electrodelines extend.
 8. The multi-qubit device of claim 5, wherein a distancebetween the first and second wire patterns is less than or equal to adistance between the first and second electrode lines.
 9. Themulti-qubit device of claim 1, wherein each of the plurality of fluxgenerating elements comprises a superconducting material.
 10. Themulti-qubit device of claim 1, further comprising an insulating layerthat has a thickness less than or equal to 100 nm and is disposedbetween the plurality of flux generating elements and the plurality ofqubits.
 11. The multi-qubit device of claim 1, further comprising aplurality of wire patterns connected to each of the plurality of fluxgenerating elements, wherein the plurality of wire patterns are disposedat a level different from a level of the plurality of flux generatingelements in the vertical direction, wherein the plurality of qubits aredisposed closer to the plurality of flux generating elements than to theplurality of wire patterns.
 12. The multi-qubit device of claim 11,further comprising: an insulating layer that is disposed between theplurality of flux generating elements and the plurality of wire patternsand comprises a plurality of via holes; and plugs that are disposed inthe via holes and interconnect the plurality of flux generating elementsand the plurality of wire patterns.
 13. The multi-qubit device of claim12, wherein the insulating layer has a thickness greater than or equalto 100 nm.
 14. The multi-qubit device of claim 1, wherein the pluralityof flux generating elements are a plurality of first flux generatingelements, wherein the multi-qubit device further comprises a third layerstructure that faces the first layer structure, the first layerstructure being disposed between the second layer structure and thethird layer structure, and wherein the third layer structure comprises aplurality of second flux generating elements that applies flux to theplurality of qubits in the vertical direction.
 15. The multi-qubitdevice of claim 14, wherein the plurality of second flux generatingelements are symmetrical to the plurality of first flux generatingelements.
 16. A quantum computer comprising the multi-qubit device ofclaim
 1. 17. A multi-qubit device comprising: a layer structurecomprising a plurality of qubits; a plurality of first flux generatingelements that are disposed under the layer structure in a verticaldirection of the multi-quit device and apply flux to the plurality ofqubits in the vertical direction; and a plurality of second fluxgenerating elements that are disposed above and on the layer structurein the vertical direction and apply flux to the plurality of qubits inthe vertical direction.
 18. The multi-qubit device of claim 17, whereineach of the plurality of first flux generating elements is symmetricalto each of the plurality of second flux generating elementscorresponding to the plurality of first flux generating elements. 19.The multi-qubit device of claim 17, wherein each of the plurality ofqubits comprises a closed loop structure and at least one Josephsonjunction provided disposed on the closed loop structure, and furthercomprises a first electrode line and a second electrode line thatextends in parallel to the first electrode line from a side of theclosed loop structure.
 20. The multi-qubit device of claim 19, whereineach of the plurality of first flux generating elements comprises afirst partially open loop structure, wherein each of the plurality ofsecond flux generating elements comprises a second partially open loopstructure, and wherein the multi-qubit device further comprises: a firstwire pattern and a second wire pattern that extends in parallel to thefirst wire pattern from the first partially open loop structure; and athird wire pattern and a fourth wire pattern that extends in parallel tothe third wire pattern from the second partially open loop structure.21. The multi-qubit device of claim 20, wherein the first and secondpartially open loop structures have a size less than or equal to a sizeof the closed loop structure.
 22. The multi-qubit device of claim 20,wherein the first and second wire patterns and the third and fourth wirepatterns extend in a direction in which the first and second electrodelines extend.
 23. The multi-qubit device of claim 20, wherein the firstand second wire patterns are disposed at a level different from a levelof the first partially open loop structure in the vertical direction,and at least a part of the first and second wire patterns extend in adirection different from a direction in which the first and secondelectrode lines extend, and/or wherein the third and fourth wirepatterns are disposed at a level different from a level of the secondpartially open loop structure in the vertical direction, and at least apart of the third and fourth wire patterns extend in a directiondifferent from the direction of the first and second electrode lines.24. The multi-qubit device of claim 17, wherein the plurality of firstflux generating elements are disposed on a substrate, wherein themulti-qubit device further comprises: a first insulating layer that isdisposed on the substrate and covers the plurality of first fluxgenerating elements; and a second insulating layer that is disposed onthe first insulating layer and covers the plurality of qubits, whereinthe plurality of qubits are disposed on the first insulating layer andthe plurality of second flux generating elements are disposed on thesecond insulating layer.
 25. A quantum computer comprising themulti-qubit device of claim
 17. 26. A multi-qubit device comprising: afirst layer comprising a plurality of qubits; and a second layer that isdisposed on the first layer, and comprises a plurality of fluxgenerating elements that apply flux to the plurality of qubits, aplurality of wire patterns that provide current to the plurality of fluxgenerating elements, and a plurality of plugs that are disposedperpendicular to the plurality of flux generating elements and theplurality of wire patterns and interconnect the plurality of fluxgenerating elements and the plurality of wire patterns, wherein each ofthe plurality of flux generating elements is integrated with acorresponding one of the plurality of wire patterns and a correspondingone of the plurality of plugs.